Method and apparatus for evaporating liquid oxygen



May 16, 1939. J. A. MATHIS ET AL METHOD AND APPARATUS FOR EVAPORATING LIQUID OXYGEN I 2 Sheets-Sheet 1 Filed March 26, 1938 Ma 16, 1939. J. A. MATHIS El AL METHOD AND APPARATUS FOR EVAPORATING LIQUID OXYGEN 2 Sheets-Sheet 2 Filed March 26, 1938 g .I a

Patented May 16, 1939 PATENT OFFICE METHOD AND APPARATUS FOR EVAP- OBATING LIQUID OXYGEN John A. Mathis and Roland W. Milan, Pinckncyville, 111.

Application March 26,

19 Claims.

This invention relates to the method and. apparatus for providing a controlled flow of gaseous oxygen by the controlled evaporation of liquid oxygen.

Heretofore a controlled flow of oxygen has been available only from cylinders in which oxygen is stored under pressure. The amount of oxygen withdrawn from cylinders has been regulated by regulators or reducing valves. The storage of oxygen in metallic cylinders under pressure is unsatisfactory not only due to the great weight of each cylinder as compared to the amount of gas it contains but also due to the danger incident to the high pressure involved. Furthermore, the weight not only makes transportation costs high, but also makes the movement of cylinders from one place to another within the establishment of the consumer a difllcult task. According to the present invention, omgen is received by the consumer in a liquid form, rather than as a gas under pressure. Liquid oxygen may be transported in containers which are relatively light in weight as compared to the usual cylinder for storing oxygen under pressure. Furthermore, oxygen in a liquid form is considerably cheaper than oxygen in a gaseous form under pressure. Evaporated liquid oxygen has still another advantage when used in an oxygen tent in that it is exceedingly cold, and therefore heavy and cumbersome refrigerating apparatus normally used to cool the interior of oxygen tents is not necessary.

An object of the invention is to provide a method and apparatus for providing a controlled flow of gaseous oxygen by evaporating liquid oxygen.

Another object of the invention is to provide a method and apparatus for applying controlled heat to liquid oxygen to evaporate the oxygen in controlled quantities.

A further object of the invention is to employ cold gaseous oxygen evaporated from liquid oxygen for use in oxygen tents without refrigerating apparatus.

A still further object of the invention is to provide in apparatus for evaporating liquid oxygen a device to prevent the heating element from becoming active until it reaches a predetermined low temperature due to the contact or close association with liquid oxygen.

These and other objects will be apparent from the following specification when taken with the accompanying drawings, in which Fig. 1 is a partial vertical section showing the apparatus according to the present invention installed on a ilask containing liquid oxygen,

1938, Serial No. 198,226

Fig. 2 is a front elevation disclosing the instrument panel of the invention,

Fig. 3 is a wiring diagram,

Fig. 4 is a vertical section of the thermostatic switch, and

Fig. 5 discloses the apparatus of the invention in operation supplying oxygen to an oxygen tent.

Briefly, the invention contemplates disposing an electric resistance heating element within a container holding liquid oxygen. Electricity from a suitable power source and controlled by a rheostat supplies energy to the heating element to evaporate the liquid oxygen. vBy varying the re sistance the heat dissipated within the liquid oxygen container from the electric heating element will vary and therefore vary the rate of evaporation of the liquid oxygen. A voltmeter, for instance, across the terminals of the heating element may be calibrated to indicate directly the rate of evaporation. Gaseous oxygen driven of! from the liquid oxygen by evaporation may or may not be passed through a bare copper coil to warm the same to room temperature. For the purpose of checking the rate of flow by the voltmeter a kinetic. flow meter is provided. A thermostatic switch is included in the heating element circuit to automatically open the heating element circuit when the temperature at the heating element rises above a predetermined degree.

Referring particularly to the drawings, the reference character I indicates the usual Dewar flask provided with the usual outlet neck 2. Secured in the cabinet 3, in which the apparatus according to the present invention is mounted, is 35 an outlet connection 4 having an internal, conical, groundsu'rface 5 for engaging with the neck 2 of the Dewar flask I. The ground surface 5 provides a gas-tight connection with the neck 2 and directs the oxygen in a gaseous form from 40 the flask I into the outlet tube 6. Sweated in the upper portion 1 of the outlet 4 is an elongated tube 8, having disposed therein an electric resistance heating element 9 and a thermostatic element ll) containing carbon dioxide or some suitable expansible and contractible fluid responsive to temperature. The thermostatidelement 10 preferably is disposed adjacent the heating element 9.

Electric power for energizing the resistance heating element 9 is obtained from a suitable source S, as shown in Fig. 3. A conductor H from the source S is connected to one terminal of a snap switch It. The other terminal of the snap switch I: is connected to one terminal of a rheostat I3. The other terminal of the rheostat I3 is connected to a conductor I4, which is in turn connected to one terminal of the resistance heating element 9. A conductor I5 from the other terminal of the resistance heating element 9 is connected to the terminal 20 of a thermostatic switch 2! under the control of the thermostatic element Ill. The heating element circuit is com pleted through the movable arm 22 of the thermostatic switch 2I to the terminal 23 and then to the conductor 24 back to the source S. A voltmeter 25 is connected across the terminals of the resistance heating element 9. It will be clear from the foregoing that the heating element circuit is under control of the snap switch I2 and the thermostatic switch 2i and that the voltmeter will indicate the variations in potential across the resistance heating element 9 caused by adjustment of the rheostat i3.

Assuming that when the snap switch i2 is closed the arm 22 of the thermostatic switch M is in engagement with the terminal 2d of the thermostatic swltch 2|] to close the heating element 9 circuit, then the heat generated in the heating element 9 will be dissipated into the interior of the Dewar flask I and will evaporate the liquid oxygen 3E9 therein. Gaseous oxygen will flow upwardly through the neck 2 to the outlet tube 6 to a twoway valve 2i. The two-way valve 3!! is arranged. to direct gaseous oxygen through a bare copper coil 22 and thence to a kinetic flow meter 33 or to icy-pass the gaseous oxygen past the coil 32 directly to the kinetic flow meter As the back and bottom of the cabinet 3 are opened, there will be a circulation of air at room temperature through the cabinet 5 which will act to warm the oxygen passing through the coils it will be understood that as liquid oxygen boils at 3U0 unless the gaseous oxygen just evaporated is passed through warming coils, it will be delivered from the outlet 34 of the flow meter 33 in a very cold state. However, as it is sometimes desirable to use the oxygen in a cold state, the two-way valve 3I is provided so that either warm or cold oxygen may be obtained.

The thermostatic valve 2i serves as a safety feature in that it opens the heating element 9 circuit when the temperature within the flask i rises to a suitable predetermined degree. Experiments have shown that F. is very satisfactory. Therefore, when all of the liquid oxygen in the flask I has been evaporated, the heat from the heating element 9 will heat up the interior of the flask I and the thermostatic element I0. When the temperature of the thermostatic element Ill reaches 0 F., the bellows 35 disclosed in Fig. 4 connected to the thermostatic element I 0 by a tube 35' are actuated to pivot the arm 36 about the flxed point M to rock the arm 22 about the fixed point 39 to move the arm 22 from engagement with the terminal 20 into engagement with the terminal. The expansion of the carbon dioxide in the thermostatic element III will result in'the bellows moving the arm 36 against the action of the spring 42, which is supported at its upper end from a rigid arm 43 by a bolt 44 and adjusting nuts 45.

It will be clear, therefore, that when the temperature adjacent the heating element it rises, the arm 22, in moving away from the contact 20, opens the heating element 9 circuit. However, at the same time the heating element 9 circuit is opened, another circuit, including the conductor 24, the terminal 23, the arm 22, the terminal til, the conductor it, a pilot light it, the conductor areas-cs till, the snap switch I2, and the conductor II, is closed. Thus, when the heating element 9 circuit opens, the pilot light 41 circuit closes, the pilot light 47 indicating that the liquid oxygen in the flask l has been completely used up. The thermostatic switch 2| is provided with a conventional magnetic device 48 for moving the arm 22 with a snap action.

As shown particularly in Figs. 1 and 2, the cabinet 3 is provided with a panel 50, on which is dis posed the control knob of the rheostat I3, the face of the voltmeter 25, the flow meter 33, the pilot light 417 and the snap switch I2. The panel 50 is also provided with a panel light 55 under the control of a snap switch The panel light i and the snap switch 52 are disclosed in the wiring diagram of Fig. 3 and are connected across the ter.- minals of the source S by the conductors ll, 53, 5Q, 55, and

When it is desired to use the apparatus according to the present invention, the tube 8 is inserted in the neck 2 of a Dewar flask l containing liquid oxygen, the weight of the cabinet 3 and the apparatus being carried by the outlet i having the ground, conical surface 5 resting on the neck 2 to provide a gas-tight seal. When a tube has been connected to the outlet B l to conduct the evaporated oxygen to the place desired and the electrical connection shown in the drawings as the conductors i l and 2d is connected to a suitable source, such as a wall outlet, the snap switch I2 is turned on. If the tube ii and the thermostatic element 9 therein have not reached a temperature of 0 the pilot light M will be energized through the conductor II, the snap switch t2, the conductor St, the conductor 46, the thermostatic switch 2|, through the contacts M, the arm 22, the contact 23, and the conductor 24, the heating element 9 circuit being open. As soon as the thermostatic element ill and tube 8 reach a temperature of 0 F. or lower, the carbon dioxide in the thermostatic element III contracts to such an extent that the spring 42 disclosed in Fig. 4 overcomes the force exerted by the bellows 35 and through the arm 36 moves the arm 22 into contact with the terminal 22. The result is that the circuit, including the pilot light 41, is opened, and the heating element 9 circuit is closed through the conductor II, the snap switch I? of the rheostat I3, the conductor I4, the conductor I5, the terminal 20, the arm 22, the terminal 23, and the conductor 24. The rheostat I3 may be adjusted to provide a temperature of the resistance heating element 9 which will produce a desired rate of flow of oxygen indicated either by the voltmeter 25 or by the kinetic flow meter 33.

In calculating the calibrations for the volt meter 25, rather than by comparison to a flow meter, it must be considered that the evaporation of the oxygen in the flask I will be due not only to the heat dissipated from the heating element 9 but also due to the constant conduction of heat through the walls of the flask I and to the conduction of heat down the tube 8. It has been found that for the standard 25 liter commercial Dewar flask the conduction of heat through the walls thereof is responsible for the evaporation of about 450 cubic centimeters of oxygen per minute and that the tube 8 is responsible for the evaporation of about 700 cubic centimeters of oxygen per minute. It is of interest to note that when the oxygen in the flask I reaches a very low level so that it is barely touching or does not touch the tube 8, there is no change in the rate of evaporation for a given setting on the thermostat IS. The reason for this is that the flask l is well insulated, and any heat within the interior of the flask l is transmitted to the liquid oxygen 3|, even though the heating element is not immersed directly into it. Because of this fact it is considered to be within the contemplation of the present invention that the heating element 9 be not limited-to being immersed in the liquid oxygen but may be anywhere within the flask I or within the walls thereof so long as the heat dissipated therefrom is substantially retained within the interior of the flask I.

No provision has been made for cutting off the supply of oxygen evaporated by the heat conducted through the walls of the flask I and down the tube 8 for the reason that the pressure generated could not be withstood by any material available for portable equipment. However, if the omen outlet should become stopped due to some accident or unforeseen reason, the pressure generated by the evaporating oxygen, either while the heating element 9 is energized or while it is not energized, will lift the outlet 4 from the neck 2, permitting the escape of pressure without damage to any of the apparatus.

The safety feature afforded by the thermostatic switch II is of considerable value, for should the omen within the flask I completely evaporate, the continual dissipation of the heat therein, considering the fact that the walls of the msk l are highly insulated, would result in a building up of heat within the flask l until damage to the apparatus would result. It will be observed from Fig. 4 that the thermostatic switch 2| is arranged so that when the carbon dioxide in the thermostatic element II is contracted, the heating ele ment 9 circuit is closed. However, the specific structure and operation of the thermostatic switch 2| disclosed is not essential, as any equivalent thermostatic switch may be used.

In l 'ig. 5 is disclosed a particular use of the invention, namely, the supplying of gaseous oxygen to an oxygen tent. The flask l is shown as disposed on a frame 8| mounted on castors 62. Projecting upwardly from the frame I are standards 3, to which are suitably clamped a pole 64, from the outer end of which is suspended an oxygen tent 65. The ozwgen tent 65 is provided with windows 86, an opening 61 in the top and an oxygen inlet attachment plate 68. As shown, the oxygen tent 65 is associated with a bed 69 in a conventional manner. A tube ll connects the outlet 3! of the evaporating apparatus with the attachment plate 68 on the oxygen tent to conduct oxygen to the interior of the tent 65. The tube II is preferably insulated to conduct cold oxygen to the interior of the tent 65 to cool the same. The present invention, due to its ability to supply cold oxygen, eliminates the necessity of refrigerating apparatus, which has heretofore been required. Inspection of Fig. 5 will disclose that the present invention comprises a simple light weight apparatus which may be readily moved from one place to another with a small amount of effort.

While the present invention is particularly adaptable for use in supplying the oxygen to oxygen tents for medical use, its use in no way is limited to providing oxygen for oxygen tents. For instance, the invention is particularly adaptable for use in submarines where large quantities of oxygen must be stored. The present invention makes possible the'availability of large supplies of oxygen with the employment of very little weight and storage space. The invention has similar utility in the supplyin of oxygen in airplanes, as well as for commercial use, such as for oxidizing purposes and the like.

It will be understood that the particular form of the invention disclosed is to be considered only as an example. Therefore, having thus described our invention, what we desire to secure by Letters Patent and claim is:

l. The method of evaporating liquid oxygen,

which comprises transferring to the same electn'cally generated heat and varying the rate of transfer of said heat to vary the rate of evaporation.

2. The method of evaporating liquid ongen, which comprises disposing an electrical resistance element in heat transferring relation to said liquid oxygen, applying an electrical potential across said element, and varying said potential to vary the rate of evaporation.

3. The method of obtaining a flow of gaseous oxygen at a desired rate, which comprises subjecting liquid oxygen to controlled heat, and varying said heat to produce the desired flow of gaseous oxygen by evaporation of said liquid owgen.

4. The method of obtaining a flow of gaseous I to a patient in an oxygen tent and refrigerating said tent, which comprises subjecting liquid oxygen to controlled heat to evaporate said liquid oxygen at a controlled rate, and conducting the gaseous oxygen into the tent, whereby heat in the tent is absorbed by the gaseous oxygen.

6. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid onwgen, a circuit connected to a source of electricity, said circuit including said heating element, and a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation.

7. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid oxygen, a circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating i element to vary the rate of evaporation of the liquid oxygen, and a voltmeter connected across said heating element to indicate the rate of said evaporation.

8. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid ongen, a circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation of the liquid oxygen, and a flow meter to indicate the rate of said evaporation.

9. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid oxygen, a circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation ofthe liquid oiwgen, a thermostatic switch associated with said heating element, connections between said thermostatic switch and said circuit to open said circuit when the temperature at said heating element reaches a predetermined degree, and means to indicate the rate oi said evaporation.

iil. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid oxygen, a circuit connected to a source or electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by the heating element to vary the rate of evaporation of the liquid oxygen, means associated with said circuit and said heating element to open said circuit when the heat at said heating element reaches a predetermined maximum, and means to indicate the rate of said evaporation.

ll. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for dis position in heat transferring relation to a supply of liquid oxygen, a circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation of the liquid oxygen, a thermostatic switch associated with said heating element, a pilot light, a circuit for said pilot light, and connections between said circuit, thermostatic switch and pilot light to open said heating element circuit and to close said pilot light circuit when the temperature at said heating element reaches a predetermined degree.

12. Apparatus for evaporating liquid oxygen, comprising an electrical heating element for disposition in heat transferring relation to a supply of liquid oxygen, a circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation of the liquid oxygen, an elongated warming tube for evaporated oxygen to pass through, and means to indicate the rate of said evaporation.

13. Apparatus for evaporating liquid oxygen, comprising heating means for disposition in heat transferring relation to a. supply of liquid oxygen, means to control the amount of heat generated by said heating means to vary the rate of evaporation of the liquid oxygen, and means to conduct evaporated oxygen from said supply of liquid oxygen.

'14. Apparatus for evaporating liquid oxygen from a container having a relatively small opening, comprising a tube for disposition through said opening into said container, an electrical heating element disposed in said tube for transferring heat to the liquid oxygenTa circuit connected to a source of electricity, said circuit including said heating element, a variable resistance in said circuit to vary the heat dissipated by said heating element to vary the rate of evaporation of the liquid oxygen, a temperature responsive elegreases a connection between said thermostatic switch and said circuit to open said circuit when the temperature in said tube at said heating element reaches a predetermined degree, means to conduct oxygen from the opening in said container, and means to indicate the rate of said evaporation.

15. A device of the character described for obtaining a flow of gaseous oxygen from a container of liquid oxygen, the container having an opening, comprising a cap for disposition over said opening, a tube projecting through said cap, means included by said cap for providing a gas-tight seal between the same and said opening, an outlet from said cap for gaseous oxygen, said tube having the lower end thereof closed, said end being within the container when said cap is over said opening, an electrical heating element within said tube, and an electrical connection from said heating element passing out of the upper end of said tube for connection to a source of electricity.

16. A device of the character described for providing a flow of gaseous oxygen from a container of liquid oxygen, the container having an opening, comprising an elongated tube, a heating element in said tube adjacent one end thereof, an electrical connection from said heating element extending out of the other end of said tube, a cap through which said tube projects providing a gas-tight connection with the opening of the container, an outlet from said cap for conducting gaseous oxygen from said opening, said tube when said cap is over said opening having its first named end projecting into the container, means for preventing the passage of oxygen through said tube, and apparatus for controlling said heating element, supported by said cap.

17. The method of obtaining a flow of gaseous oxygen from liquid oxygen which comprises the projection into liquid oxygen of a conductor .of heat whereby the heat from the atmosphere surrounding the portion of said conductor out of said liquid oxygen is conducted down said conductor into said liquid oxygen to evaporate the same.

18. The method of obtaining a flow of gaseous oxygen by the evaporation of liquid oxygen which comprises the insertion into the liquid oxygen of heat supplying means and varying the heat supplying characteristics of said means to vary the evaporation of said liquid oxygen.

19. The method of administering gaseous oxygen to a patient in an oxygen tent and refrigerating said tent which comprises evaporating liquid oxygen and conducting the gaseous oxygen into the tent whereby heat in the tent is absorbed by the gaseous oxygen.

' JOHN A. MATHIS.

ROLAND W. MILAN.

DISCLAIMER 2,158,458.Jhn A. Mathis and Roland W. Milan,

' APPARATUS FOR EVAPORATING LI UID OXYGEN.

Pinclmeyville, Ill. METHOD AND Patent dated May 16,

1939. Disclaimer filed September 30, 1940, by the patentees. Hereby enter this disclaimer to claims 1, 2, 3, 4, 6, 13, 17, and 18 in said specification. 

